Welcome to the Solar System

A Celestial Alignment

Why do they line up?

Image from: ganymede.nmsu.edu/tharriso/ast110/class05.html

Moons also orbit in the same plane

Jupiters equitorial bands show the eliptic (tilt = 0)

Image: http://www.jb.man.ac.uk/astronomy/nightsky/Jupiterjuly10.jpg

Orbits in the Ecliptic

This also includes ring systems!

The Solar Disk

• Seen from a 100 AU

• Solar system is a dusty disk

The Layout of the Solar System• Large bodies in the

Solar System have orderly motions– planets orbit

counterclockwise in same plane

– orbits are almost circular

– the Sun and most planets rotate counterclockwise

– most moons orbit counterclockwise

The Layout of the Solar System

• Planets fall into two main categories– Terrestrial (i.e. Earth-like)

– Jovian (i.e. Jupiter-like or gaseous)

Mars Neptune

Terrestrial Jovian

Mars and Neptune to Scale

The Layout of the Solar System

• Swarms of asteroids and comets populate the Solar System

Comets are found in two main Zones:

The Kuiper Belt

The Oort Cloud

The Oort cloud goes from 5000 to 50,000 AU or further!

When Comets are disturbed from their orbits..

• They end up in eliptical orbits..• Encounters with Jovian Planets speed them

up or slow them down…• The Oort Cloud is the “shell” of slow

moving comets at aphelion• Speeds at aphelion might be a few cm/sec! • If and when they approach the Sun, the

move much faster!

They Also Grow Tails…

Image from APOD (credit and copyright Jimmy Westlake)

Not everything fits perfectly

• The line between planet and comet is not clear!

• Pluto, Quoar, Viruna, Xenia, and Sedna are all Kuiper Belt objects (KBO’s)

• Or the Solar system has at least 13 planets…or 8 major planets and 5 + minor planets!

Check out: http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html Artists conception of Xenia and the Solar

System…100AU from Sun. Note the 44

degree tilt of orbit.

Quoar’s Orbit

Meet some new family members

How out does the solar system go?

A Few (more) Exceptions to the Rules…

• Both Uranus & Pluto are tilted on their sides.• Venus rotates “backwards” (i.e. clockwise).• Triton orbits Neptune “backwards.” • Earth is the only terrestrial planet with a

relatively large moon.• Density decreases from Mercury outward,

but Earth is more dense than any other planet!

A Brief Tour of the Solar System -- Motions

What is density?

density = mass/volume

typical units: [ g/cm3]

Density of water is defined as 1 g/cm3.

Density of typical Metal is 10 g/cm3

A Brief Tour of the Solar System – Composition

A Brief Tour of the Solar System – Summary

Spacecraft Missions--categories

1. Flyby – spacecraft “flies by” a world just once

2. Orbiter – spacecraft orbits the world it studies– longer-term study is allowed

3. Lander/Probe – spacecraft lands on the surface of the world or plunges through its atmosphere

4. Sample Return – spacecraft returns to Earth with a sample of the world it has studied

These types of mission are listed in order of increasing cost.

Missions to Other Worlds

Upcoming missions:

Deep Impact:

Crashed into comet Temple 1 July 4 2005

Mars Reconnaissance Orbiter: Low orbit..one meter surface resolution! Launched Aug

12..Arives Nov 06.

New Horizons: Orbiter to Pluto/Charon leave 2006 – arrive 2020!

Highlights of coming attractions• Mercury’s extreme days and nights, tall steep cliffs, and large

iron content

• Venus’s extreme greenhouse effect

• Earth as an oasis of life

• Evidence on Mars for a past, wet era

• Jupiter’s hydrogen and helium atmosphere and its many moons

• Saturn’s rings and its moon Titan, which is larger than Mercury

• Uranus and its moons: a system tipped on its side compared to the other planets

• Neptune’s largest moon, Triton, with nitrogen “geysers” and a “backward orbit”

• Pluto as a member of the family of Minor Planets!